1. Technical Field
The present invention relates to electronic elements, circuit substrates, electronic devices, a method for manufacturing electronic elements, a method for manufacturing circuit substrates, and a method for manufacturing electronic devices.
2. Related Technology
Among methods for mounting an electronic element on a circuit substrate having a wiring pattern, a flip-chip method is known. In the flip-chip method, a bump is disposed on a surface of an electronic element, the surface having the bump formed thereon is opposed to a circuit substrate having a wiring pattern, and the bump is connected to the wiring pattern, to thereby connect the electronic element to the circuit substrate.
FIG. 6 shows one example of an electronic element 61 having a bump that is formed by an electroplating method over an electrode pad through UBM (Under Bump Metal), wherein a dielectric film 53 is formed over an electrode pad 52, UBM layers 54 and 56 are formed thereon, and an electrode post 58 composed of Ni and a bump 59 composed of Sn—Ag are further formed on the UBM 56 by an electroplating process.
In the conventional method for forming the bump 59 by an electroplating process, the surface area of the UBM layers 54 and 56 is generally the same as the bottom area of the bump 59. Also, the size of the bump 59 has become smaller to accommodate the size of the substrate 51a and the number of the electrode pads 52. For this reason, the bottom area of the bump 59 has become smaller, and the surface area of the UBM layers 54 and 56 has become smaller accordingly. The adhesion of the materials that compose the UBM layer 54 and the dielectric film 53 is lower than the adhesion of the materials composing the UBM 54 and the UBM 56 or the UBM 56 and the bump 59. When the surface area of the UBM 54 becomes smaller, the adhesion of the dielectric film 53 and the UBM 54 may become lower compared to the adhesion at the interface of the other layers. In this case, at the time when or after the electronic element 61 is mounted on the circuit substrate having the wiring pattern, peeling at the interface between the UBM 54 and the dielectric film 53 would likely occur.
The present invention is made in view of such circumstances, and provides electronic elements, circuit substrates, electronic devices, a method for manufacturing electronic elements, a method for manufacturing circuit substrates, and a method for manufacturing electronic devices, which improve adhesion of electrode pads and bumps.